1. Field of the Invention
This invention relates to an infrared light designed for use with infrared imaging equipment. Specifically, this invention relates to a high intensity light for use on aircraft or other vehicles and utilizes infrared (xe2x80x9cIRxe2x80x9d) LASER diodes.
2. Description of the Related Art
Military and law enforcement personnel regularly use night vision imaging systems (xe2x80x9cNVISxe2x80x9d) to support covert operations. NVIS systems utilize infrared light amplification techniques to allow the user to see terrain, objects, people, and targets in conditions of near total darkness. NVIS equipment is frequently augmented by infrared lighting. The IR lights cast a bright beam of infrared light that extends the viewing area of the NVIS system but cannot be detected by the unaided eye, preserving the covert nature of night vision operations.
Aircraft commonly use landing lights to provide illumination during taxi, take-off, and landing when visibility is reduced by darkness or adverse weather conditions. Similarly, helicopters use searchlights to aim a beam of light in a desired direction to illuminate areas of interest or targets. High intensity IR lights have previously been installed on aircraft for this purpose in conjunction with NVIS equipment, but they suffer from several disadvantages. Prior high intensity IR lights typically use sealed beam or halogen incandescent lamps coupled with a xe2x80x9cblack glassxe2x80x9d filter that blocks visible light while passing infrared light. Such high intensity IR lights generate a substantial amount of heat due to the low efficacy of incandescent lamps and the visible light energy trapped in the lamp housing by the infrared light filter. This condition is made worse by the need to use high-wattage lamps to overcome the inefficiencies of the lamp and filter to achieve the high infrared light output needed for landing lights and searchlights.
The high temperatures generated by prior infrared high intensity lights may have many detrimental effects. For example, the operating life of the incandescent lamps is considerably reduced. In fact, the lab-rated lamp life of some prior incandescent lamp-filter IR high intensity lighting systems may be as low as 50 hours, with an even lower life expectancy in the harsh aircraft environment. This increases the risk of a lamp failure at a critical time during covert operations. The high temperatures can also cause premature failure of other materials, such as cracking of the filter due to thermal stress and accelerated weathering of filter sealing materials. If either the filter or the seal were to fail, high intensity visible light could escape, compromising covertness.
A limitation of incandescent lamp-filter IR high intensity lighting systems is that the high operating temperature increases the thermal signature of the light. If the light""s thermal signature is too high, the light may be visible to thermal imaging systems and equipment used by opposing personnel. It should be further noted that the black glass NVIS filter does not filter out all visible frequencies of light. As a result, the prior high intensity IR light may have a visible red glow, also compromising covertness.
As previously noted, the low efficacy of incandescent lamps combined with the low efficiency of IR filters has necessitated the use of high-wattage lamps to overcome these drawbacks. As a result, 200-watt incandescent lamps are commonly used for aircraft landing lights and searchlights, burdening the aircraft""s electrical system. Since the prior landing and searchlights are so prone to failure it is common to install two or more lighting systems on the aircraft, further taxing the aircraft""s electrical system.
Alternative lighting systems have been devised to overcome some of these obstacles. For example, Meyers U.S. Pat. No. Re. 33,572 discloses an infrared light beam projector for use with a night vision system. However, infrared high intensity lights such as those used for aircraft landing lights and searchlights require a much higher level of light than can be achieved through the teachings of Meyers. Laser diodes have been previously used in vehicular applications, such as Scifres U.S. Pat. No. 5,713,654 which discloses a centralized lighting system for vehicular instrument lights, marker lights, and brake lights. However, the high intensity light requirements of landing lights and searchlights obviate use of the teachings of Scifres. A co-owned and pending patent application, U.S. patent application Ser. No. 09/217,221, xe2x80x9cIR Diode Based High Intensity Light,xe2x80x9d offers an alternate means for generating high intensity infrared light. However, application Ser. No. 09/217,221 differs significantly from the present invention. The present invention uses LASER infrared diodes rather than infrared light emitting diodes, resulting in coherent infrared light as opposed to non-coherent infrared light, and includes means for combining infrared light emissions from two or more infrared light sources.
There is a need for a light which provides a beam of high intensity infrared light, has a long operating life, does not generate high temperatures, has a low thermal signature, and operates with reduced power requirements compared to prior IR high intensity lighting systems.
This invention is directed to a light which provides a beam of high intensity infrared light without the need for resorting to inefficient and power-hungry incandescent lights and xe2x80x9cblack glass filters.xe2x80x9d
Specifically, the present invention includes two or more LASER infrared light emitting diodes. xe2x80x9cLASERxe2x80x9d is an acronym for xe2x80x9clight amplification by stimulated emission of radiation.xe2x80x9d Lasers are used in the creation, amplification, and transmission of a narrow, intense beam of coherent light. The coherent light produced by a laser differs from ordinary light in that it is made up of waves all of the same wavelength and all in phase, whereas ordinary light contains many different wavelengths and phase relations.
If an array of LASER infrared light emitting diodes (xe2x80x9cLIDsxe2x80x9d) is employed, the IR light""s intensity will be greater. An array also carries an inherent benefit of redundancy in that the remaining LIDs will continue to operate if one LID should fail, reducing the risk of total failure of the high intensity IR light at a critical time during a covert operation.
The LIDs are mounted to a heat sink for temperature stabilization. The heat sink serves to extend LID life by maintaining the LID""s operating temperature within the manufacturer""s specification. The infrared light emitted by the LIDs is coupled to an optical transmission means, such as machined or molded light pipes, or preferably optical fibers. An optical positioning plate receives the infrared radiation from the optical transmission means and concentrates the radiation of the individual LIDs into a single beam, providing a xe2x80x9cpointxe2x80x9d source of infrared light. An aspheric lens is situated such that its focal plane is placed at the light emitting surface of the optical positioning plate. The aspheric lens receives the beam of light emitted by the optical positioning plate and collimates the radiation, resulting in a radiant intensity greater than six. A conical reflector, such as a polished aluminum reflector, may optionally be placed between the optical positioning plate and the aspheric lens to further direct the infrared light emitted by the optical positioning plate, resulting in increased light-collection efficiency.
Electrical power is connected to a control circuit that conditions the voltage and current to a level compatible with the LIDs. The control circuit may be mounted inside the housing, or may be located remotely. The control circuit provides sufficient electrical power to activate the LIDs while preventing over-driving of the LIDs.
The high intensity IR light may include a housing to contain internal components of the light. The housing may include mounting points to facilitate installation and mounting of the infrared high intensity light.
The present invention comprises a high intensity infrared light, comprising: a housing; two or more LASER infrared diodes arranged inside said housing; means comprising a heat sink for receiving heat from said LASER infrared diodes; means for collecting and transmitting the infrared light radiated by said LASER infrared diodes; means for receiving and combining the infrared light from said transmitting means into a single beam of infrared light and to radiate the beam of light from a light emitting surface; and an aspheric lens situated such that the focal plane of said aspheric lens is placed at the light emitting surface of said combining means, wherein said aspheric lens is adapted to receive the beam of infrared light emitted by the combining means and to collimate said beam of infrared light.
These and other features will become better understood with reference to the following description, appended claims, and accompanying drawings.